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(No Model.)

B. R. GURLEY.

DISTANCE INSTRUMENT.

No. 359,073. Patented Mar. 8, 1887.

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UNITED STATES PATENT OFFICE.

REVERE B. GURLEY, OF \VASHINGTON, D. C.

DISTANCE-VINSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 359,073, dated March 8,1887.

I Application filed September 15, 1885. Serial No. 17?;194. (No model.)

To aZZ whom, it may concern.-

Be it known that I, REVERE R. GURLEY, a citizen of the United States,and a resident of \Vashington, (the Soldiers Home,) in the District ofColumbia, have invented certain new and useful Improvements in MeasuringDevices, of which the followingis a specification.

My invention relates to instruments for measuring distances, and it hasfor its object the production of a measuring-instru ment that shall besimple of construction and reliable in use, and which shall be basedupon a principle whereby complex calculations may be dispensed with inthe measurement of distances.

The principle of which I make use in the construction of mymeasuring-instrument is the well-known geometrical law that lines drawnparallel to one side of a triangle, if sufficiently extended,producesections of the two other sides that are proportional. The mannerin which I employ this law will clearly appear from the followingdescription, with reference to the accompanying drawings, in whichFigure 1 shows a plan view of astructure in which my invention isembodied; Fig. 2, a side elevation of the same with the pivot andbaseline bar partially in section, and Fig. 3 enlarged transversesection through the baseline bar and telescope-holder. Fig. 4 is anenlarged detached view looking in the direction of thearrow, Fig.1. Fig.5 is a modification. Fig. 6 is a diagram illustrating the principle ofmy invent-ion and the mode of practicing the same.

Mounted upon a tripod or otherwise is a base-plate, B, having abase-line bar, B, pivoted thereto so as to be substantially paralleltherewith. I have shown a conical pin, 0, upon the under side of thebar, fitted into a corresponding socket in block 0, which is secured toor made in one piece with the baseplate B. Any other suitable method ofpivoting may, however, be employed. From the other end of the barprojects downward a short block, D, which supports the bar B on thetrack Z. Above the block D is a block within the bar pivoted forrotation around a vertical axis. This block is engaged by theadjusting-screw S, locked against longitudinal motion by the blocks 1?and Q. The latter are free to move along the tracks parallel to theprime position of the bar. Thus the line of the screw is alwaysperpendicular to the prime position of the bar. Any method of securingthe screw may, however, be employed which does not introduce too greatan error. Thus, for example, D and Q may be used, the former passingthrough the baseline and the latter pivoted to the base-plate. Thisinvolves an error of about .00005; or D may be free to movelongitudinally within the bar and P and Q be secured to the base-plate,due-error of less than .00002.

The amount of motion of the bar may be determined by the distancebetween the threads of the adj usting-screw and the amount of rotationof same, or in any other suitable manner.

The base-line bar B is slotted longitudinally for the reception of thetraveling nut 01., to which is secured the carriage E for thesighting-instrument. The axis of the latter makes, with the line of thebar B, an invariable (preferably a right) angle. A screw-rod, a, lockedat the ends of the bar B against longitudinal motion, engages thetraveling nut, and by turning said screw the sighting-instrument maybeadjusted to any desired position upon the base-line bar B. By graduatingthe bar, or otherwise, the distance of the sighting-instrument from theend of the bar may be determined. If, now, an object be sighted throughthe sighting-instrument at the end of the bar 0, and the bar be thenmoved through any angle, the object may be again sighted by travelingthe instrument, by means of the screw-rod, a suitable distance along thebar.

In Fig. 6 the base-line bar B is represented in its normal and itsangular positions, and is divided into feet, (or other units ofmeasure,) at a a b b c c d d, 850., these points marking the distancesof one two three four, &c., feet, (or other units of length,)respectively, from the pivotal point C. If now an object, a, be sightedthrough the sighting-instrument at G, and the bar B be then movedthrough an angle, 0 Ca a, to the position indicated by the broken 7line, then the object may be again sighted by moving thesighting-instrument by means of the screw-rod to a, for since 0=Oaa, ais the point of intersection with Ct of the line a" a, which makes withCt an angle equal to that included between the axis of thesighting-instrument and the bar, (the angle between the two being thesame in both cases.) If the sighting-instrument be moved twice thedistance from the pivotal point C-viz., to the point Z) on the bar-anobject, 6, will be accurately sighted, the distance of which from O istwice as great as that of a from the same point, and if the distance ofthe sighting-instrument from thepivotal point he made three four..., orn times as great as the distance of a from the same point the distanceof the objects dd, &C., will be three four....., or n times as great asthat of on, since thehomologous sides of thesimilar triangles Coda Obb00 c O dd, &c. are proportional. It only remains to determine the angle0. For simplicity, suppose tCa :90 degrees, Oa=5, 280 feet, (Ja'=l foot,Ct (the length of the bar B, from the pivotalpoint (l to the point ofapplication of the adjustingscrew) to be 52.80 inches. Let the axis ofthe sighting-instrument be perpendicular to the line of the bar B, andlet Ct 16 be considered a right-angle triangle, since the length of thebase-line bar is necessarily very small compared with the distancesmeasured by the instrument, and the adjustment of the bar is thereforealso very small, and the are described by said bar is to all practicalpurposes a straight line and may be considered as at right angles to thebase-line,thusgreatly simplifying the solution of the problem withoutcausing material error. Then Ca a and Gt tare both right-angletriangles, and their homologous sides are proportional; hence Ca (la/'3it Ct, which, with the above figures, becomes 1 5,280 :1 w 52.80, whencex or tt=.0l inch. Thus the angle 0 is determined by its sine, and if abar of the length of 52.80 inches be moved .01 inch, each foot ofmovement along such a bar from the pivotal point determines a distanceof 1 mile in the field, and fractions and multiples of feet upon the bardetermine like fractions and multiples of miles in the field.

It is evident that the demonstration applied for simplicity to rightangles applies equally to any angles whatever between thesightinginstrument and the bar, and also to any scale, whether of feetand miles or otherwise.

It is evident that the sighting-instrument may be pivotally mounted inthe bearing and a graduated circle be attached, so that the altitude ofobjects may be easily deduced.

Compasses, levels, and all other attachments ordinarily applied tosurveying-instruments may be applied in an obvious manner.

I claim 1. A measuring-instrument consisting of a base-1i ne bar pivotedat one end, a micrometerscrew connected to the other end of the bar toadjust the same, and a sighting-instrument adjustable longitudinally onthe said bar, substantially as described.

2. In a measuring-instrument, the combina tion, with a pivoted base-linebar, of a sighting-instrument maintained upon said bar at a fixed angleand adjustable longitudinally thereon, and a definitely-threadedadjusting-screw for determining the angular adjustment of said bar,substantially as described.

3. A measuring-instrument consisting of a base-line bar pivoted at oneend, a micrometer adjustingscrew for moving the other end of the bar, asighting-instrument on the said bar, and a screw for adjusting the saidsighting-instrument longitudinally on the said bar, substantially asdescribed.

In testimony whereofI have signed my name to this specification in thepresence of two subscribing witnesses.

R. R. GURLEY.

Vitnesses:

GEO. W. BEALL, \VM. B. YOUNG.

